Effect of thickness and substrate temperature on structure and optical band gap of hot wall-deposited CuInSe2CuInSe_{2} polycrystalline thin films

The copper indium di selenide $(CuInSe_{2})$ Compound was prepared by direct reaction of high-purity elemental copper, indium and selenium. $CuInSe_{2}$ thin films were prepared on to well-cleaned glass substrates by hot wall deposition technique. The X-ray diffraction studies revealed that all the deposited films are polycrystalline in nature, single phase and exhibiting chalcopyrite structure. The crystallites were found to have a preferred orientation along the (1 12) direction. The SEM analysis indicated that the films are polycrystalline in nature. The composition of the chemical constituents present in the deposited $CuInSe_{2}$, thin films has been determined using energy dispersive X-ray analysis (EDX).Structural parameters of $CuInSe_{2}$, thin films coated with higher substrate temperatures were also studied. As the substrate temperature increases the grain size increases. Simultaneous TG-DTA analysis has been done for $CuInSe_{2}$ bulk and an endothermic, reaction is observed near the melting point of the compound. Optical transmittance spectrum of the hot wall-deposited CuInSe2 thin films of different thicknesses deposited at three different substrate temperatures were obtained. As the thickness of the film and the substrate temperature increases, the optical band gap decreases. The refractive index of the $CuInSe_{2}$ thin films are found decreasing with the incident photon wavelength

Structural and Transport Properties of Hot Wall Deposited CuInSe2CuInSe_2Thin Films and the Fabrication of CuInSe2CuInSe_2 Based Solar Cells

Films of $CuInSe_2$ were deposited onto glass substrates by a hot wall deposition method under thermodynamic equilibrium condition using bulk $CuInSe_2$ as a source material. All the deposited CuInSe2 films were found to be polycrystalline in nature exhibiting the chalcopyrite structure with the crystallite orientation along (101), (112), (103), (211), (220), (312) and (400) directions. The crystallites were found to have a preferred orientation along the (112) direction. Microstructural parameters of the films, such as grain size, dislocation density, tetragonal distortion and strain have been determined. The grain sizes in the films have been found in the range of 89 to 244 nm. Hall effect studies have been carried out on the hot wall deposited $CuInSe_2$ thin films. Hall voltage has been measured as a function of temperature in the range 80 to 460 K. The obtained positive Hall voltage indicates that the prepared $CuInSe_2$ films are of p-type nature with holes as majority charge carriers. The Hall co-efficient is found to decrease with increase in film thickness. The carrier concentration in $CuInSe_2$ films is found to be of the order of $10^{17} cm^{-3}$. The carrier concentration is observed to increase with increase in film thickness. The Hall mobility is found to increase very slowly in the low temperature region from 80 to about 215 K, and then rapidly with increase in temperature above 215 K. The mobility is found to increase with increase in film thickness. The dependence of $T^{3/2}$ law for Hall mobility indicates that scattering on ionized impurities is predominant in the temperature region above 215 K in hot wall deposited $CuInSe_2$ thin films. The grain boundary potential (Eb) of $CuInSe_2$ thin films of different thickenesses has been evaluated. The barrier height is observed to decrease with increase in carrier concentration indicating the presence of partially depleted grains in $CuInSe_2$ films. $CuInSe_2$-based solar cells with CdS as buffer layer were fabricated. The fabricated solar cells were illuminated using 100 $mW/cm^2$ white light under AM1 conditions. The current and voltage were measured using an optical power meter and an electrometer, respectively. The solar cell parameters, open circuit voltage (V_{oc}), short circuit current (Isc), series resistance ($R_s$), shunt resistance ($R_{sh}$), power maximum ($P_{max}$) and fill factor (FF) were determined

Structural characterization of DC magnetron-sputtered TiO2 thin films using XRD and Raman scattering studies

Titanium dioxide films have been deposited using DC magnetron sputtering technique onto well-cleaned p-silicon substrates at an oxygen partial pressure of 7 x 10(-5) mbar and at a sputtering pressure (Ar + O-2) Of I X 10(-3) mbar. The deposited films were calcinated at 673 and 773 K. The composition of the films as analyzed using Auger electron spectroscopy reveals the stoichiometry with an 0 and Ti ratio 2.08. The influence of post-deposition annealing at 673 and 773 K on the structural properties of the titanium dioxide thin films have been studied using XRD and Raman scattering. The structure of the films deposited at the ambient was found to be amorphous and the films annealed at temperature 673 K and above were crystalline with anatase structure. The lattice constants, grain size, microstrain and the dislocation density of the film are calculated and correlated with annealing temperature. The Raman scattering study was performed on the as-deposited and annealed samples and the existence of Raman active modes A(1g), B-1g and E-g corresponding to the Raman shifts are studied and reported. The improvement of crystallinity of the TiO2 films was also studied using Raman scattering studies. (C) 2003 Elsevier Ltd. All rights reserved

Optical constants of DC magnetron sputtered titanium dioxide thin films measured by spectroscopic ellipsometry

Optical constants of DC magnetron sputtered $TiO_2$ thin film have been determined by Spectroscopic Ellipsometry in the photon energy range 1.2 to 5.5 eV at room temperature. The measured dielectric-function spectra reveal distinct structures at energies of the E1, E1 + \bigtriangleup 1 and E2 critical points are due to interband transitions. The root mean square roughness of the magnetron sputtered $TiO_2$ thin films evaluated by ex-situ atomic force microscopy is 5.8 nm. The Dielectric constant values were found to be substantially lower than those for the bulk $TiO_2$. The dielectric related Optical constants, such as the refractive index, extinction coefficient, absorption coefficient and normal incidence of reflectivity determined from the spectroscopic ellipsometry data are presented and analyzed. The optical constants of the films were also determined using the optical transmittance measurements and the results were discussed

Influence of thermal annealing on the composition and structural parameters of DC magnetron sputtered titanium dioxide thin films

Titanium dioxide films have been deposited using DC magnetron sputtering technique. Films were deposited onto RCA cleaned p-silicon substrates at the ambient temperature at an oxygen partial pressure of $7 \times 10^{-5}$ mbar and sputtering pressure of $1 \times 10 ^{-3}$ mbar. The deposited films were annealed in the temperature range 673-873 K. The structure and composition of the films were confirmed using X-ray diffraction and Auger electron spectroscopy. The structure of the films deposited at the ambient was found to be amorphous and the films annealed at 673 K and above were crystalline with anatase structure. The lattice constants, grain size, microstrain and the dislocation density of the film are calculated and correlated with annealing temperature

Hydrophilic polymer coated monodispersed Fe3O4 nanostructures and their cytotoxicity

Surface functionalized monodispersed Fe3O4 magnetic nanoparticles were synthesized by the polyol method. Surfactants were used to control size, shape and agglomeration of the magnetic nanoparticles during the preparation. The size of these nanoparticles was in the range of 10\u201330 nm as observed in transmission electron microscopy (TEM). The formation of monodispersed shapes was controlled by varying the surfactants without changing the reaction conditions. The x-ray diffraction (XRD) pattern validates the phase purity and cubic structure even after the addition of surfactants. The functional groups were observed from Fourier transform infrared (FTIR) spectroscopy analysis, confirming the surface modification with polymer molecules in the polyol medium. The saturation magnetization value decreases from 89 to 59 emu g 121 for the surfactant coated Fe3O4 nanoparticles and it also shows superparamagnetic behavior at room temperature. Cell viability rate and percentage of dead cells were accurately identified in human breast carcinoma cell lines using in vitro cell viability experiments, which confirms that pristine and surfactant coated Fe3O4 nanoparticles are non-toxic and can be used for biomedical applications

Analysis on superhydrophobic silver decorated copper Oxide nanostructured thin films for SERS studies

The present work demonstrates the superhydrophobic and Surface Enhanced Raman Spectroscopy (SERS) active substrate performance of silver coated copper oxide (Ag@CuO) nanostructured thin films prepared by the SILAR process. Super hydrophobic substrates that combine super hydrophobic condensation effect and high enhancement ability of Ag@CuO nanoflowers are investigated for SERS studies. The possible growth mechanism for the formation of nanoflower arrays from nanospindles has been discussed. Morphology and crystallinity of the Ag@CuO thin films are confirmed using FESEM and XRD. The results obtained in the present study indicate that the as-deposited hydrophobic nanospindles structure converts to super hydrophobic nanoflower arrays on annealing at 200 degrees C. The Ag@CuO super hydrophobic nanoflowers thin film based SERS substrates show highly enhanced Raman spectra with an EF value of 2.0 x 10(7) for (Rhodamine 6G) R6G, allowing a detection limit from a 10(-10) mol L-1 solution. The present study may provide a new perception in fabricating efficient super hydrophobic substrates for SERS, suggesting that the fabricated substrates are promising candidates for trace analysis of R6G dye and are expected to be widely used as highly sensitive SERS active substrates for various toxic dyes in the future. (C) 2016 Elsevier Inc. All rights reserved